Triggering electronic devices for the control of electromagnetic actuating devices



Jan. 8, 1963 P R M GOIN 3,072,045

TRIGGERING ELECTRONIC DEVICES FOR THE CONTROL 0F ELECTROMAGNETIC ACTUATING DEVICES Filed May 27, 1959 United States Patent OI 3,072,045 TRIGGERING ELECTRONIC DEVICES FOR THE CONTROL OF ELECTROMAGNETIC ACTUAT- ING DEVICES Pierre Raymond Michel Goin, Fontenay-sous-Bois,

France, assignor to Compagnie des Machines Bull (Societe Anonyme), Paris, France Filed May 27, 1959, Ser. No. 816,160 Claims priority, application France June 2, 1958 3 Claims. (Cl. 10193) A device of this type is particularly applicable to I on the wheel by the mechanical striking action of a hammer actuated by the said device at a given instant depending upon the character to be printed. The present invention is also applicable to actuating devices for high-speed printing mechanisms which print characters in the form of dots or by the impression of sections of characters or signs.

In so-called flying-Wheel printing machines in which the striking is produced by the energisation of an electromagnet, the movement of a character during the striking has the disadvantage of producing on the paper a trail of print which is larger as the printing wheel rotates at a higher speed. In order to obviate this trail effect, the striking must be very rapid and return devices are generally provided with the object of returning the striker hammer as rapidly as possible as soon as the printing has been effected. These devices consist either of resilient abutments acting by rebound, or of return springs which are cocked by the striking movement of the hammer. In order to overcome the resistance set up to the movement of the hammer by the return members, it has been found necessary to provide more powerful actuating electromagnets, which must therefore be of larger dimensions and thus act less rapidly. The return of the striker hammer is also produced to some extent by the rebound thereof on the printing wheel itself, but this return effect is successive powerful electric pulses of opposite polarities.

These devices are very rapid and permit'striking movements whose duration does not exceed several tenthousandths of a second. In order to supply the rapid and powerful electric pulses necessary for actuating such devices, there are employed, for example, so-called pushpull electronic circuits or circuits in which amplifier tubes are controlled by pulses supplied by electronic flipfiop circuits having one stable state, which are capable of supplying, from a single electric pulse, two consecutive powerful electric pulses of opposite polarities, but these circuit arrangements are costly, heavy and cumbersome. The present invention has for its object to obviate these disadvantages by means of a simple and economic circuit arrangement which permits of utilising the first the angular position of the shaft.

data to be printed. sented by the coded data received from the analysing de- .vice AN and in accordance with the indications supplied 3,072,045 Patented Jan. 8, 1963 winding of the actuating device of a second current pulse,

in the opposite direction to the first and corresponding to the second half-cycle of the said damped oscillation.

For a better understanding of the invention, an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 is a diagrammatic illustration of the main elements of a high-speed printing machine comprising a continuously rotating character wheel,

FIGURE 2 is a diagram illustrating the principle of a device for the production of pulses which operates with a damped oscillating discharge, designed in accordance with the invention,

FIGURE 3 is a characteristic oscillogram representing a damped oscillating discharge,

FIGURE 4 shows an electromagnetic actuating device of the polarised blade type, and

FIGURE 5 shows an electromagnetic actuating device of the dynamic actuation type.

In the diagrammatic illustration of FIGURE 1 there are shown in very simplified form, the main elements of a continuously rotating high-speed printing machine and the connections between these elements. In this illustration, a motor M drives with a continuous rotational movement through a shaft A1 at least one character wheel R. The said wheel has formed on its periphery characters disposed in any predetermined order. An extension A2 of the shaft AI drives a synchronising device S which transmits to a decoding device D indications derived from An analysing device AN transmits to the decoding device D coded indications emanating from the analysing of record cards or tapes, or from any other device which transmits, in coded form, In accordance with the signs repreby the synchronising device, the decoding device D transmits a control pulse to an actuating device AC at a given instant, depending upon the character to be printed. The said actuating device then actuates a hammer MT which strikes an inked ribbon RE against a record sheet P which receives from the printing wheel R the impression of a character in the printing position at the instant of the striking action.

The device for actuating the hammer MT consists, for example, of a polarised electromagnetic actuating device of the type illustrated in FIGURE 4 or 5.

In the device of FIGURE 4, the striker hammer MT is mounted on a rod 2 fast with a flexible blade 3 fixed at a point 4. The rod 2 is also fast with a blade 5 having high magnetic permeability, which is fixed at a point 6 and is adapted to oscillate within an induction coil BI which is maintained between two pole pieces 7 and 8 consisting of thin magnetic sheets or of a material of hi h permeability having low losses at high frequencies. The pole pieces 7 and 8 are maintained between two blocks 9 and 10 of metal of high permeability, which are fixed to a high power permanent magnet 11. The pole pieces 7 and 8 each receive respectively north magnetic polarity (N) and south magnetic polarity (S) imparted by the field of the permanent magnet. If a direct current .field produced by the permanent magnet 20.

3 of given direction is passed through the induction coil BI, the blade 5 is magnetised and the portion 12 of the said blade develops a north or south magnetic polarity depending upon the direction of the current in the coil. it, for example, the portion 12 is given south polarity, this portion will be strongly attracted by the pole piece *7, which has north polarity, and repelled by the pole piece 3, which has south polarity. Consequently, the upper portion of the blade 5 is thrown towards the left and pushes the striker hammer MT against the inked ribbon RE, which applies the printing sheet F against the printing wheel R. A reversal of the current in the induction coil BI produces in the blade 5 an opposite magnetic polarity and an inverse movement of the hammer MT, which is then pushed to the right. The oscillating assembly consisting of the blades 3 and 5, the hammer MT and the rod 2 has a natural oscillation frequency 7 which is preferably very much lower than the oscillation frequency of the electric circuit supplying the pulses. A damping device 16, for example of the mechanical friction or air type, is provided to effect a rapid damping of the oscillations of the movable assembly.

FIGURE 5 illustrates a construction of an actuating device of the dynamic type, of which the well known principle is frequently employed to actuate diaphragms of loudspeakers. In the illustrated example, a ring-shaped permanent magnet '20 is maintained between two plates 21 and 22 having high magnetic permeability. The plate 21, has formed in its centre an aperture through which there can move a tube 32 supporting a coil 33. A central magnetic core 23 is fast with the plate 22 and canalises through the coil 33 the lines of force of the magnetic A rigid cone 24 adapted to the tube 32 is fast with a rod 25, which is secured to the striker hammer MT. The tube 32 is centered in the air gap 34 of the magnetic circuit by a deformable support 28 which permits displacements of the coil 33 in the said air gap. Disposed opposite the.

striker hammer MT are an inked ribbon RE, the paper sheet or tape F and the character wheel R of the printing machine. When an electric current is passed through the coil 3.3, the hammer 26 is pushed towards or away from the printing wheel, depending upon the direction of the current.

The diaphragm (FIGURE 2) shows a circuit designed to supply electric pulses to a polarised electromagnetic actuating device. A high-voltage current, for example of 275 volts, is applied to the said circuit through two terminals marked respectively +I-IT for the +275 volts and HT for the -275 volts, the latter being connected to earth. Two terminals CH supply a low-voltage current, for example at 6 Volts, for heating the filament F of a triggering gas tube TD of the type universally known under the name thyratron. The positive high-voltage terminal is connected to the anode A of the tube TD through a switch I, a resistance R and the coil E of a polarised electro-magnetic actuating device. A condenser C is connected on the one hand to the resistance R and on the other hand to earth, which corresponds to the HT terminal. In a machine utilising a device according to the invention, the time available for recharging the condenser C may be relatively very short. In this case, the value of the resistance R will be as low as possible, but it will have a sufficient value to limit the charge current of the condenser and to reduce the wear on the contacts of the switch I. In other cases, the available time for recharging the condenser being relatively long, the resistance R may have a higher value and ensure sufficient insulation of the oscillation circuit from the high voltage to enable the switch I to be omitted. In addition, the voltage applied at +HT for recharging the condenser may vary and may be adjusted in accordance with the desired striking force. The energy stored in the said condenser is expressed in joules by the relation W= /2CV in which C is the capacity in farads of the condenser and recharging of the condenser C, if desired, outside the instance when the condenser can be discharged to actuate the printing member. The screen EC and the cathode CT of the tube TD are connected together and to earth. A unidirectional element DD (diode or rectifier) is connected between the anode A of the tube TD and the cathode (earth) of the said tube. A current source SC supplies a negative bias to the control grid GC of the tube through a resistance RP. This grid receives through a connecting condenser CL by way of a line L pulses which control the triggering of the tube and which are transmitted by the decoding device D (FIGURE 1). The condenser C being charged and the tube TD receiving at its control grid GC a triggering pulse, the condenser C is discharged through the coil E (BI, FIGURE 4, or 33, FIGURE 5) of the actuating device. The circuit is closed as follows: Earth, condenser C, coil E, anode Act the tube TD, cathode CT of the tube and return through earth. When the total volume of the ohmic resistances R, in the discharge circuit of the condenser is not excessive, that is to say, when the circuit is not completely damped by the said resistances, the discharge of the condenser is effected with damped oscillation, the frequency characteristic f of which in cycles per second is given by the following relation:

in which L is expressed in henries, C in farads and R which is the resistance of the discharge circuit (tube TD and coil E), in ohms. FIGURE 3 illustrates a series of damped oscillations whose cycle P is equal to Only the first half-cycle AA of the oscillation triggered by the discharge of the condenser passes through the tube TD, which blocks the second half-cycle. The second halfcycle AB of the oscillation, which is of opposite direction to the first, cannot pass through the triggering tube TD, which forms a barrier, and it therefore passes through the succeeding circuit, which differs partly from the circuit through which the first half-cycle passes: condenser C, earth, diode DD, coil E and return to the condenser. The triggering pulse sent to the control grid GC of the tube TD ceases, in principle, before the end of the first half-cycle of the oscillation, but it may without disadvantage be prolonged for a part of the second half-cycle without preventing deionisation of the tube. This is because, the second half-cycle being of opposite polarities to the first, the voltage drop produced by the passage of the current of this second half-cycle through the diode DD sets up between the anode and the cathode of the tube TD a voltage of opposite polarity to the voltage which existed during the first half-cycle and deionises the tube. A third half-cycle CA in the same direction as the first (FIGURE 3) cannot pass through the tube TD, which is deionised, or through the diode DD, which is so directed as to suppress this half-cycle. The damped oscillation is therefore interrupted. The energy transferred to the condenser by the inductance of the coil E- towards the end of the second half-cycle partly recharges the said condenser and reduces the time and the energy necessary for completing the recharging of the said condenser. It is obvious that the above-described circuit arrangement may also be employed with a triggering transistor arrangement, that the diode DD may be replaced by a thermionic valve or by a cold-cathode valve, that the coil of the actuating device may be disposed at another point of the discharge circuit of the condenser, and that any substitutions or modifications of form or detail may be made, depending upon the conditions of the applications, without departing from the spirit of the invention.

I claim:

1. A printing mechanism comprising a continuously rotatable wheel provided with a set of characters, a striker hammer fast with a polarised electromagnetic actuating device comprising an inductive winding in which there can flow an electric current whose direction determines the direction of movement which is imparted to the striker hammer, a condenser, means for charging the said condenser, an ionisable gas tube provided with a control electrode, the condenser and the inductive winding of the actuating device being connected in series with the gas tube, a unidirectional rectifier element connected in parallel with the gas tube in such manner that the direction of flow of the current through the said unidirectional element is opposite to the direction of flow of current through the gas tube when it is ionised, means for applying an electric pulse to the control electrode of the gas tube at an instant determined in accordance with the character to be printed, the said pulse having the effect of ionising the said tube and of triggering in the circuit a damped oscillation, of which the first half-cycle, during the discharge of the condenser, passes through the winding of the actuating device in a direction such that the striker hammer is actuated to print the selected character, while the second half-cycle of the said oscillation passes through the winding of the actuating device in an opposite direction to the first half-cycle and moves the striker hammer away from [the character Wheel during the re-charging of the condenser through the rectifier element, the gas tube being deionised by the voltage drop across the terminals of the said rectifier element.

2. Electromagnetic actuating device according [to claim 1, wherein the actuating member consists of a polarised magnetic blade which is adapted to move, in accordance with its polarity, between the poles of a magnet, the polarity of the said blade being determined by the direction of the current flowing through a coil which constitutes the energising circuit of the actuating device.

3. Electromagnetic actuating device according to claim 1, wherein the actuating member consists of a movable coil adapted to shift perpendicularly to a magnetic field in a direction which is determined by the direction of the current through the said coil.

References Cited in the file of this patent UNITED STATES PATENTS 2,411,898 Shelling Dec. 3, 1946 2,692,551 Potter Oct. 26, 1954 2,907,900 Hoyer Oct. 6, 1959 2,907,929 Lawson Oct. 6, 1959 

1. A PRINTING MECHANISM COMPRISING A CONTINUOUSLY ROTATABLE WHEEL PROVIDED WITH A SET OF CHARACTERS, A STRIKER HAMMER FAST WITH A POLARISED ELECTROMAGNETIC ACTUATING DEVICE COMPRISING AN INDUCTIVE WINDING IN WHICH THERE CAN FLOW AN ELECTRIC CURRENT WHOSE DIRECTION DETERMINES THE DIRECTION OF MOVEMENT WHICH IS IMPARTED TO THE STRIKER HAMMER, A CONDENSER, MEANS FOR CHARGING THE SAID CONDENSER, AN IONISABLE GAS TUBE PROVIDED WITH A CONTROL ELECTRODE, THE CONDENSER AND THE INDUCTIVE WINDING OF THE ACTUATING DEVICE BEING CONNECTED IN SERIES WITH THE GAS TUBE, A UNIDIRECTIONAL RECTIFIER ELEMENT CONNECTED IN PARALLEL WITH THE GAS TUBE IN SUCH MANNER THAT THE DIRECTION OF FLOW OF THE CURRENT THROUGH THE SAID UNIDIRECTIONAL ELEMENT IS OPPOSITE TO THE DIRECTION OF FLOW OF CURRENT THROUGH THE GAS TUBE WHEN IT IS IONISED, MEANS FOR APPLYING AN ELECTRIC PULSE TO THE CONTROL ELECTRODE OF THE GAS TUBE AT AN INSTANT DETERMINED IN ACCORDANCE WITH THE CHARACTER TO BE PRINTED, THE SAID PULSE HAVING THE EFFECT OF IONISING THE SAID TUBE AND OF TRIGGERING IN THE CIRCUIT A DAMPED OSCILLATION, OF WHICH THE FIRST HALF-CYCLE, DURING THE DISCHARGE OF THE CONDENSER, PASSES THROUGH THE WINDING OF THE ACTUATING DEVICE IN A DIRECTION SUCH THAT THE STRIKER HAMMER IS ACTUATED TO PRINT THE SELECTED CHARACTER, WHILE THE SECOND HALF-CYCLE OF THE SAID OSCILLATION PASSES THROUGH THE WINDING OF THE ACTUATING DEVICE IN AN OPPOSITE DIRECTION TO THE FIRST HALF-CYCLE AND MOVES THE STRIKER HAMMER AWAY FROM THE CHARACTER WHEEL DURING THE RE-CHARGING OF THE CONDENSER THROUGH THE RECTIFIER ELEMENT, THE GAS TUBE BEING DEIONISED BY THE VOLTAGE DROP ACROSS THE TERMINALS OF THE SAID RECTIFIER ELEMENT. 